Added sscache to improve compilation times

.azure/install-rust.yml

@@ -37,3 +37,6 @@ steps:
       rustc -Vv
       cargo -V
     displayName: Install Rust
+
+  - bash: echo "##vso[task.setvariable variable=RUSTC_VERSION;]`rustc --version`"
+    displayName: Set rustc version in env var

.azure/install-sccache.yml

@@ -0,0 +1,41 @@
+# This template installs sccache (Shared Compilation Cache)
+# More info: https://github.com/mozilla/sccache
+
+steps:
+
+  - bash: |
+      set -e
+      curl -Lfo sccache.tar.gz https://github.com/mozilla/sccache/releases/download/0.2.10/sccache-0.2.10-x86_64-apple-darwin.tar.gz
+      tar -xzf sccache.tar.gz
+      cp sccache-*/sccache /usr/local/bin/
+    displayName: Install sccache (macOS)
+    condition: and(succeeded(), eq(variables['Agent.OS'], 'Darwin'))
+
+  - bash: |
+      set -e
+      curl -Lfo sccache.tar.gz https://github.com/mozilla/sccache/releases/download/0.2.10/sccache-0.2.10-x86_64-unknown-linux-musl.tar.gz
+      tar -xzf sccache.tar.gz
+      sudo cp sccache-*/sccache /usr/local/bin/
+    displayName: Install sccache (Linux)
+    condition: and(succeeded(), eq(variables['Agent.OS'], 'Linux'))
+
+  - bash: |
+      curl -Lfo sccache.tar.gz https://github.com/mozilla/sccache/releases/download/0.2.10/sccache-0.2.10-x86_64-pc-windows-msvc.tar.gz
+      tar -xzf sccache.tar.gz
+      move sccache-* sccache
+      echo "##vso[task.prependpath]%CD%\sccache"
+    displayName: Install sccache (Windows)
+    condition: and(succeeded(), eq(variables['Agent.OS'], 'Windows_NT'))
+
+  - bash: |
+      set -ex
+      sccache -V
+    displayName: sccache version
+
+  - bash: |
+      set -ex
+      echo "##vso[task.setvariable variable=RUSTC_WRAPPER;]sccache"
+      SCCACHE_ERROR_LOG=`pwd`/sccache.log RUST_LOG=debug sscache --start-server
+      sscache -s
+      cat sccache.log
+    displayName: Start sccache  

azure-pipelines.yml

@@ -41,6 +41,7 @@ jobs:
     - template: .azure/install-rust.yml
     - template: .azure/install-cmake.yml
     - template: .azure/install-llvm.yml
+    - template: .azure/install-sscache.yml
     - task: CacheBeta@0
       inputs:
         key: |